Inorganic chemical scales often form in oil and gas production equipment and cause limitations on the oil and gas handling capacity of that equipment. Prevention or removal of the scale is expensive and sometimes difficult. Calcium carbonate and calcium sulfate scales can usually be removed by conventional methods. Barium and strontium sulfate scale, on the other hand, cause severe problems. They are a major factor in the loss of production from oil wells in many fields.
Present efforts are directed toward washing the equipment with aqueous solvents such as acids or toward physically removing the scale by mechanical means. These methods are expensive, often difficult to conduct and rarely effective on barium or strontium sulfate. In a few cases, aqueous solutions of complexing agents are used to dissolve the barium or strontium sulfate scale. However, these solvents are also expensive and are not fully effective. Therefore, a novel, inexpensive method of removing scale from oil and gas production equipment is needed. Liquid membrane systems provide a novel way of removing scale from oil and gas production equipment. Although others have used liquid membrane systems for pollution control in the removal of heavy metals from waste water streams, liquid membrane systems proposed for use to remove scale is a novel concept. Use of liquid membrane systems for selective ion transfer has been proposed. Indeed, a patent was issued for the use of the selective membrane system to remove pollutants from water. It issued Sept. 29, 1981 to Li as U.S. Pat. No. 4,292,181. Li in U.S. Pat. No. 4,259,189 issued Mar. 31, 1981, disclosed novel liquid membrane formulations for use in high temperature applications. In U.S. Pat. No. 4,014,785 issued to Li et al. on Mar. 29, 1977, novel liquid membrane formulations were proposed for use in the treatment of sourwater feed streams. Singhal et al. disclosed novel liquid membrane formulations in U.S. Pat. No. 3,969,265 issued July 13, 1976. Via this patent, novel liquid membrane formulations were developed to provide stable emulsions; these compositions were proposed for use in a liquid membrane sour water treating process wherein a waste water stream contained ammonium sulfide.
Until now, no one has used liquid membrane systems to remove scale from oil and gas production equipment.